Field of the Invention
Embodiments of the present invention relate to an output buffer, a source driver and a display device including the same, and a method of using the same.
Discussion of the Related Art
A source driver may include latches for driving source lines of a liquid crystal panel and storing data, a level shifter for shifting a voltage level of the stored data, a digital-to-analog converter for converting the voltage-level-shifted data into an analog signal, and an output buffer for amplifying the analog signal. The source driver may output the amplified signal to the source lines.
When a voltage is applied to a liquid crystal of a pixel only in one direction upon driving the liquid crystal panel, degradation of the liquid crystals may be accelerated. To this end, an inversion method, in which an image data voltage applied to the liquid crystals is periodically inverted to periodically have an opposite polarity, is used.
Such an inversion method includes frame inversion, line inversion, and dot inversion. Frame inversion is a method in which voltage polarities of all pixels in the liquid crystal panel are inverted at the same time. Line inversion is a method in which lines connected to adjacent scan lines are alternately inverted. Dot inversion is a method in which inversion is performed on a pixel-by-pixel basis.
Output buffers of a source driver may alternately output signals having opposite polarities every period according to a given inversion method. Signals to control such operation of the output buffers may be referred to as inversion polarity signals (POL). In order to output signals having opposite polarities, each output buffer of the source driver may include a multiplexer including switches that perform a switching operation in response to the inversion polarity signals.
Each output buffer should supply a large current to the switches of the multiplexer thereof in order for the output voltage to reach a predetermined level within a line time determined and/or based on resolution of the liquid crystal panel. However, when a large current is supplied to the switches, a large amount of heat may be generated due to the resistance of the switches. For this reason, when the output voltage of the output buffer changes, the slew rate of the output buffer may decrease.